Many new drugs, including vaccines, proteins, peptides and DNA constituents, have been developed for better and more efficient treatment for disease and illness. Especially due to recent advances in molecular biology and biotechnology, increasingly potent pharmaceutical agents, such as recombinant human insulin, growth hormone, follicle stimulating hormone, parathyroid hormone, etanercept, and erythropoietin are available. However, one significant limitation in using these new drugs is often a lack of an efficient drug delivery system, especially where the drug need to be transported across one or more biological barriers at therapeutically effective rates and amounts.
Most drugs are orally administered. However, most protein drugs (e.g., proteins, peptides, and/or nucleic acids, etc.) cannot be effectively adsorbed in this manner due to their degradation in the gastrointestinal tract, poor absorption in intestinal membrane, and/or first pass breakdown by the liver. To circumvent such difficulties, parenteral administration may be employed. Typically such administration relies on injection of the drug into the patient's circulatory system or muscle tissue using standard syringes or catheters. Unfortunately, needle injection often provokes needle phobia, substantial pain, and/or local damage to the skin in many patients. Similarly, withdrawal of body fluids (e.g., whole blood) for diagnostic purposes provokes comparable discomforts. Moreover, and especially where needle injection-based access to body fluids is required for long-term drug administration or long term monitoring of an analyte, numerous challenges arise. For example, needles tend to clog when left over a prolonged period in a patients vascular system. Also, mobility of the patient is generally limited.
Alternatively, transdermal delivery may be employed which usually relies on passive diffusion of a drug across the skin. However, transdermal delivery is often not broadly applicable as the skin presents a relatively effective barrier for numerous drugs (the outermost layer of skin, the stratum corneum, represents a major barrier to drugs with a molecular weight of greater than about 500 Dalton). Once a drug reaches the dermal region (below the epidermal layer), the drug diffuses rapidly to deep tissue layers and other parts of the system via blood circulation. To improve the rate of drug delivery through the skin, chemical enhancers, iontophoresis, electroporation, ultrasound, and heat elements have been used. However, and depending on the particular drug, such techniques frequently fail to provide a therapeutic level of delivery. Worse yet, such techniques will sometimes provoke undesirable skin reactions for long term drug delivery.
Still other known transdermal drug delivery methods include needle-free particle or liquid injection, which are thought reduce incidence of contamination and accidental injuries. However, liquid injection frequently causes pain, and in some cases even sub-dermal hemorrhage. Similarly, exact and consistent ballistic particle injection is typically difficult to achieve and can also cause micro-bleeding in some cases.
Alternatively, micro-needle drug delivery may be employed in which microscopic needles are used that are prepared by micro-fabrication procedures common in the semiconductor industry. Most of such micro-needle devices are designed for drug delivery through a hollow interior of a needle or along an outer surface of a solid needle. However, most of these needles are made from brittle silicon materials, and needle breakage while the needle is inserted in the skin and/or removed from the skin is frequently encountered, especially with inexperienced users. Other micro-needle devices are used as skin perforators which require subsequent patch drug application. However, such administration often results in inconsistent drug dosages, inconvenient usage, and sometimes even in infections.
Therefore, although there are various methods and devices for drug administration known in the art, all or almost all them suffer from one or more disadvantages. Among other things, currently known methods and devices fail to allow controlled administration drugs, to provide prompt initiation and cut-off of drug delivery with improved safety and efficiency, and convenience. Thus, there is still a need for improved methods and devices to overcome the difficulties outlines above.